The present invention relates to lubricant compositions containing a soluble titanium-containing material, having beneficial effects on properties such as deposit control, oxidation, and filterability in, for instance, engine oils.
Current and proposed specifications for crankcase lubricants, such as GF-4 for passenger car motor oils, and PC-10 for heavy duty diesel engines specify increasingly stringent standards to meet government specifications. Of particular concern are sulfur and phosphorus limits. It is widely believed that lowering these limits may have a serious impact on engine performance, engine wear, and oxidation of engine oils. This is because historically a major contributor to phosphorus content in engine oils has been zinc dialkyldithiophosphate (ZDP), and ZDP has long been used to impart antiwear and antioxidancy performance to engine oils. Thus, as reduced amounts of ZDP are anticipated in engine oils, there is a need for alternatives to impart protection against deterioration in one or more of the properties of engine performance, engine wear, and oxidation of engine oils. Such improved protection is desirable whether or not ZDP and related materials are included in the lubricant. Desirable lubricants may be low in one or more of phosphorus, sulfur, and ash, that is, sulfated ash according to ASTM D-874 (a measure of the metal content of the sample).
U.S. Pat. No. 6,624,187, Schwind et al., Nov. 4, 2003, discloses lubricating compositions, concentrates, and greases containing the combination of an organic polysulfide and an overbased composition or a phosphorus or boron compound. Metals which can be used in the basic metal compound include (among others) titanium.
U.S. Pat. No. 5,968,880, Mathur et al., Oct. 19, 1999, discloses lubricating composition, functional fluids and greases containing certain thio-phosphorus esters. Boron antiwear or extreme pressure agents can be present, which can be a borated overbased metal salt. Examples of the metals of the basic metal compound include (among others) titanium.
U.S. Pat. No. 5,811,378, Lange, Sep. 22, 1998, discloses metal containing dispersant viscosity improvers for lubricating oils, comprising the reaction product of a hydrocarbon polymer grafted with an α,β-unsaturated carboxylic acid and a nitrogen and metal containing derivative of a hydrocarbon substituted polycarboxylic acid. The metal can be selected from (among others) titanium.
U.S. Pat. No. 5,614,480, Salomon et al., Mar. 25, 1997, discloses lubricating compositions and concentrates including an oil of lubricating viscosity, a carboxylic derivative, and an alkali metal overbased salt. Also disclosed are antioxidants which can be an oil-soluble transition metal-containing composition. The transition metal can be selected from (among others) titanium.
Titanium in the form of surface-modified TiO2 particles has also been disclosed as an additive in liquid paraffin for imparting friction and wear properties. See, for instance, Q. Xue et al., Wear 213, 29-32, 1997.
It has now been discovered that the presence of titanium, supplied, for instance, in the form of certain titanium compounds, provides a beneficial effect on one or more of the above properties. In particular, such materials as titanium isopropoxide impart a beneficial effect in one or more of the Komatsu Hot Tube Deposits screen test (KHT), the KES Filterability test, the Dispersant Panel Coker test (a test used to evaluate the deposit-forming tendency of an engine oil) and the Cat 1M-PC test.